1. Field of Invention
The present invention relates to the photoelectric technology field, and more particularly to a high-power light-emitting diode (LED) driving circuit.
2. Related Art
Two driving modes are provided to light the current high-power LED chips. One is a DC power supply constant current driving method, in which the DC power is directly introduced into the LED for use. This method is a basic mode for lighting the LED, and the working principle is that the LED lamp is lit as long as VF basic voltage and IF current requirements of the LED are met. In order to achieve the optimal luminance, the maximum value of the VF is normally used to drive the LED, with a main disadvantage of causing the LED chip to generate a high temperature above 250° C. and accelerating the aging or burning at the high temperature. The LED lamps are usually used in enclosed space without the function of dissipating heat by air convection, which requires a large area of aluminum with a high cost as a heat-dissipating plate to guide and dissipate the heat, resulting in an extra cost. If the heat is not suitably guided and dissipated, the LED may have the problem of high temperature aging, and the luminance will be quickly reduced, or the LED may even be burnt due to the high temperature, thereby increasing the high material cost. The other mode is a DC power supply pulse width modulation (PWM) constant current driving method, which needs to use an integrated circuit with a high price to generate a modulated pulse and control the current, so the cost of the circuit is too high. In addition, in order to satisfy the light-emitting luminance of the LED chips, it is necessary to provide a current of 150-350 mA to LED chips. Such a high current forces the LED chips to generate a high temperature of 250° C. at the same time in the process for converting electric energy into light energy. Therefore, it is necessary to add a large area of aluminum to guide the heat dissipation; otherwise, the LED will immediately be aged due to the high temperature and the luminance is reduced, or will be burnt at the high temperature.